Underground storage tanks (“USTs”) for fuel and oil are commonly used, and from time to time may be prone to unintended leakage. Nearly 600,000 federally regulated USTs exist in the United States, and approximately 6,000 leaks are recorded annually as reported by the U.S. Environmental Protection Agency. As such, it is desirable to detect and monitor groundwater in situ in the vicinity of USTs.
Detection of organic compounds can be performed using various sensor technologies, including acoustic-wave, optical and resistive technologies. However, when used without pre-concentration, real-time sensor technologies can detect only some relevant analytes at the required concentration levels, but others are hard to detect, such as benzene which may require detection at levels in the order of 5 ppb (5 μg/L). While sample pre-concentration in the gas phase is a well known, a need remains for pre-concentration of volatile organic compounds in the aqueous phase.
Sensors are known for determining benzene concentrations at low levels is the gas phase, but not in water. The use of traditional analysis methods requires technicians to visit the field, preserve the samples and then ship samples to a lab. Typically, results for these traditional analyses are not reported for two or more weeks. An improved method of monitoring dissolved hydrocarbons in groundwater is desired.